Low density cellulose materials



Patented Aug. 8, 1939 UNITED STATES ATENT OFFC LOW DENSITY CELLULOSEMATERIALS Bruce W. Manning, Grafton, Ill., assignor to Illinois PowderManufacturing 00., St. Louis, Mo., a corporation of Illinois 8 Claims.

This invention relates to improvements in lowdensity cellulosematerials, and more particularly to an improved low density productadapted for use as an absorbent ingredient of explosives, for

.example, those of the types containing a liquid high explosiveingredient. The present'application constitutes a continuation of anapplication filed by the present applicant December 9, 1935, and bearingSerial No. 53,598.

10 An object of the invention is attained in the production of alow-density cellulose material such as will enable meeting the demandfor bulky low density permissible powders such as are employed in themining industry. This type of explosive must in nearly all cases be ofthe type known as Ammonia Permissibles, in the production of which ithas become well nigh impossible with existing bulking or absorbentmaterials, to obtain the low density desired by the trade, withoutsacrificing strength, sensitivity and powder fume classification.

In keeping with the foregoing demand, the present invention has as animportant object, the attainment of a bulking or absorbent materialwhich will enable the production of explosives of the stated class, aswell as those of other types, without any sacrifice in strength andsensitivity, and resulting in a distinct improvement in the fumeclassification, i. e., a gas resulting from explosive combustion whichis characterized by a substantially lower volume and proportion ofnoxious gases than is the case with heretofore existing explosives ofthis type, employing other bulking ingredients.

In keeping with the foregoing, it is a major objective of the presentinvention to improve the fume classification of certain explosives ofexisting types, by reduction of the carbon monoxide content of the fume.

Yet another object of the invention is attained in an ability, throughcompounding the improved absorbent material of the present inventionwith other ingredients, to employ a higher proportion of ammoniumnitrate as well as increased amounts of liquid explosive such asnitroglycerin, so as to produce, for any given density of explosive, astronger and more sensitive product.

Yet another object of the invention is to meet in an improved manner,the existing demand for explosive cartridges of standard size, but ofsuch bulk as will provide a maximum number of cartridges per case ofgiven weight; accordingly the present objective may be stated asrealized by an explosive characterized by a substantially lower weightstandard cartridge, and hence a greater number of cartridges or unitsper standard case.

Yet another object of the invention is attained in an improvedpulverulent cellulose absorbent or bulking material having a lowerdensity than heretofore prevailing products for comparable purposes, andwhich, in spite of an extremely low weight, does not undergo anymaterial impairment of form, shape or bulk of its particles on wettingby liquids, for example, the liquid explosive ingredients characterizingcertain types 10 of dynamites. I

The foregoing and numerous other objects will clearly appear from thefollowing detailed description of the materials and processescharacterizing the present invention. 15

The novel ingredient principally characterizing the present inventioneither as utilized of itself, or as mixed or compounded with otheringredients, consists of a cellulose material of extremely light weight.Whatever be the form in 20 which this is supplied to the trade, themanner of its incorporation into soundproofing items and constructionmaterials such as wallboard, as well as the other manifoldconstructional and industrial uses, will be apparent to those skil ed inthe 25 several arts to which they pertain.

After numerous and exhaustive experiments with a variety of materialsprimarily cellulose in nature, I have discovered that the pith of manyof the plants of the family Malvaceae, popularly 30 known as the mallowfamily, produces upon suitable treatment to be described, a pulp or mealwhich is admirably suited for the purpose noted. The plant familyMalvaceae embraces three subfamilies usually designated as Malva, Altheaand 35 Lavatera, all characterized by a stalk containing a spongy orporous pith, which upon a cleaning and purifying treatment, produces acellulose material capable of being comminuted to produce either a pulpor a meal of almost feathery char- 40 acteristics and substantiallylower in density than such products as bagasse, balsa wood and productsheretofore used for the purposes noted. I have found the plants of thegenus Hibiscus to be particularly suited for the purpose described,

and of the plants of this genus, Hibiscus militaris,

popularly known as the-halberd leaved rose malparticularly upon slightmagnification, over any of the other so-called light weight absorbent orbulking materials heretofore used in the produc--' tion of highexplosive compositions. In addition to the several species heretoforeenumerated, there have also been found suitable for the purpose ofproduction of the cellulose bulking material or absorbent of the presentinvention, the several species of Hibiscus known as coccineus,moscheutos, oculiroseus, incanus, diversi/olius, acitleatus andgrandiflorus. The foregoing is of course not intended as an exhaustiveenumeration of species of the genus Hibiscus, nor of those suitable forthe purpose of preparation of the improved absorbent material. Thespecies noted,- in addition to all of the herbaceous perennials of thefamily, these being preferred for the present purpose, have, however,been found to contain a desirable pith structure in comparatively pureform, and to possess the characteristic cellular structure of theHibiscus.

In addition it is to be understood that many of the hybrid varietiesderived from plants of the Hibiscus family, are suitable for the notedpurpose. An example of such a hybrid is a modification of Hibiscuslasiocarpus, being a plant derived from this species and found presentlyin the State of California. hence referred to, at least locally,asHibiscus Cali'form'cus. It is of course obvious that any two species canbe crossed, and a hybrid formedtherefrom. It is accordingly to beunderstood that any such hybrid derived directly or indirectly from theknown species, will, so long as it possesses the characteristic mallowpith structure, be suitable for the present purpose. It is further to benoted that, although all of the several species enumerated are knownbotanically, so far as has been revealed by exhaustive plant study andresearch, no member of the mallow family has heretofore been known inthe trade or industry, for any use whatsoever. Accordingly it isdistinctly within the scope of the present invention to include anyprepared and comminuted cellulosic material derived from the pith of themallow family, which material has been produced in reasonable quantitiesby this applicant, and packaged for distribution and sale.

In the recovery of the pulp, it is preferred that the stalks of theplant be cut and allowed to dry, following which the bark and morefibrous portions of the stalk are readily removable as by employingknown mechanical decorticating processes. The inner portions of thestalk, comprising principally the heart or pulp, may then be ground in amill, for example, one of a type ordinarily'used to prepare ivory meal,gypsum and similar substances, the grinding beingcarried to a finenessapproximating 20 mesh, and the resulting ground product treated with 1%NaOH solution. Following this treatment the pulp is thoroughly washedwith water, following which it is treated with HCl of low concentration,for example, a 1% solution, after which it is washed and thoroughlydried. It is entirely possible to separate the pith and fiber byutilizing water alone, in which case the material may be ground to passa 20 mesh screen, repeatedly washed with water until a good separationis obtained. Although satisfactory and economically feasible, dependingupon water 'costs, the water treatment usually requires slightly moretime, and offers a little advantage over the treatmentfirst described,utilizing NaOI-I and HCl. It will be noted that, in lieu of the"treatment by NaOH,

soda ash has been found to give substantially the same results,affording an excellent separation and a considerable saving of time andwater.

As illustrating one possible use of the product of myinvention in anexplosive composition, the following is noted as a preference for theproduction of a low density dynamite;

-An explosive produced inac'cordance with the foregoing, will providethe following results when packed in the form of a cartridge 1 by 8",which, for convenience of reference herein, may be referred to as astandard cartridge:

Cartridge weight grams 79. 5 Cartridge count sticks per case 285Sensitivity inches 6 Rate of detonation ft./sec 5340 The powder iseasily packed into a firm stick, which shows after a substantial periodof time, no evidence of shrinkage. As providing a basis of comparison ofdensities, it may here be noted that two well known widely distributedproducts of comparable formula, except for a different ab:- sorbent orcellulose ingredient, average respectively 219 and 250 cartridges orsticks per case.

In a consideration of explosives of the type herein discussed by way ofexample, the approximate practical limits for the use of the mallow pulpcharacterizing the present invention, are substantially as appear in thefollowing tables indicating, respectively, lower and upper limits in theproportion of this ingredient:

Nitroglycerin 10. 0 14. 5 Sodium nitrate 13. 0 4. 5 Ammonium nitrate 75.0 55. 5 Mallow pulp 1. 0 25. 0 Chalk 1. 0 1. 0

For purposes of providing a single tabulation ascribing practical limitsin an explosive of the type under discussion, the following is given Percent Nitroglycerin 5-15 Ammonium nitrate 40-85 Sodium nitrate 0-20Sodium chloride 0-20 Mallow pulp Q. 1-25 Asindicative of the densityrange afforded by the foregoing formulae, standard size 1 x 8")cartridges of the explosives may be produced therefrom within a range ofweights of grams to 145 grams.

It will be understood, however, that in explosives or other compositionsof matter in which ahigher percentage or proportion of cellulose or acellulose absorbent is customarily employed, the permissible percentageof such material may substantially exceed the highest figure given forthe novel product of the present invention. Such limits are to beunderstood o l ES be ng those prescrbed by reasons of reaction, flamepropagation, optimum explosive mixtures, etc., but that no limits needbe ascribed, up to and including for any physical reason. Otherwiseexpressed, the mallow pulp material characterizing the presentinventionmay be utilized with or 7 without added ingredients, depending upon theintended purpose.

In the preparation of the novel material such as mallow pith meal, anaverage density of the comminuted pith meal has been noted assubstantially less than .1 gram, this figure often at-v taining a valueas low as .076 gram, and varying up to .094 gram. The figures here givenrepresent the, approximate weight in grams of 1 cc.

of the material under discussion, based on a determination under 25 lbs.pressure. Among the more suitable low density materials heretoforeemployed for the purposes primarily anticipated for the present, theremay be mentioned bagasse Many advantages accrue from the use of thebulking materials here described, even though it be not desired toutilize the material in a form having its lowest density. Otherwiseexpressed, in case there is desired a material having the advantageousphysical characteristics of the products disclosed, the mixtures thereofmay be readily controlled in density without necessarily varying theproportion of mallow pulp. This is possible since the ground materialmay be varied in density between limits of the order of .076 for thepure carefully cleaned and ground pith, to 213-215, the latter figuresrepresenting the approximate density of the bark alone as cleaned andprepared from Hibiscus militaris or Hibiscus lasiocarpus. It will beobvious to those skilled in the art, whether the material is utilized inexplosives or otherwise, that any desired density of the absorbent orcellulose ingredient may be obtained between the limits mentioned,merely by varying the mixture of materials derived respectively from thebark and from the pith.

It is an important feature and result arising out of the use of theabsorbent material herein described, that it permits of the productionof explosive compositions in which the total carbonaceous material isrelatively less, and the oxygen-carrying salts are substantiallygreater, for an explosive of a given density, than is the case with anyexisting explosive composition of comparable type heretofore known inthe'trade. It results from this fact that the combustion on explosionproduces a relatively high volume of carbon dioxide and a relativelylower volume of carbon monoxide, the latter being the principal noxiousgas upon which the Bureau of Mines classifications are based. Forreasons arising out of the ability to use my new bulking or absorbentmaterial, it becomes possible for the first time to employ a higherproportion of ammonium nitrate, for example, as well as a higherproportion of nitroglycerin, than in comparable explosives of heretoforeexisting types, in any given density. Consequently, it is possible toproduce for a given density,'a stronger and more sensitive By way ofillustration of the improvements attained in a reduction of the volumeand proportion of noxious gases in the fume, the following results arepresented as typifying the improvements attained by the use of mallowpith in place of bagasse, the latter having been selected for comparisonas being one of the lowest density absorbents in prevalent use inexplosives of comparable type:

Ingredients A i B i C Nitroglyoerin i5 00 15.00 15.00 Ammonium nitrate56 50 55.00 60.00 Sodium nitrate. 10 00 10.00 ll 00 6 50 15. 00

Volume of poisonous gases formed by 680 grams of .each

Liters A 87.85 B 120.69 C 54 .24

In the above tabulation, sample A represents a standard productheretofore produced by the manufacturer of the explosive within thepresent invention, while sample B is a well-known product of comparabledensity offered by a competing manufacturer, and sample C is essentiallythe same as sample A except for slight adjustments due to substitutionof the mallow pith for the bagasse heretofore employed. It is apparentfrom a comparison of the above results, that by the use of mallow pithas an absorbent it is possible for the first time to produce a lowerdensity explosive than those heretofore prevalently offered to the tradeor otherwise known to this applicant, and at the same time attain aproduct in which the volume of poisonous gases formed upon combustion,is materially lower than in the case of prevailing, comparableexplosives.

In order to enable a comparison of the three samples A, B and C supra,on a basis of their fume analyses, the following is presented to showthe relative percentage volumes of the different gaseous ingredientsresulting from combustion:

Analysis of gases From the foregoing it will appear that whileexplosives of heretofore prevalent and standard type and designated asAmmonia Permissibles, show about equal volumes, in the fume, of CO2 andCO in one instance, and in another a materially,greater proportion of COthan of CO2, the explosive formed in accordance with the presentinvention is characterized by a fume analysis in which the CO issubstantially three-fifths of the volume of CO2, and in any case,distinctly less than three-fourths of the volume of C02.-

From this it becomes evident that an improved result is presented to theart, in this material reduction in proportion of noxious gases. It maybe noted that no HzS was found in any of the fume analyses of the threesamples above scheduled.

Since the present description is merely illustrative and not to beregarded as limiting, it is to be understood that the process employedin preparing the raw material and in its recovery from its naturalsources, may be varied substantially. as may be the type of explosive orother substance in or with which the low density cellulose product maybe incorporated or utilized, all without departing from the intendedscope of the claims hereunto appended.

I claim as my invention:

1. A bulking material adapted as an absorbent for use in explosives, andconsisting ess'entially of cellulose, and including'in substantial part,the purified and ground pith of a plant of the family Malvacae.

2. As an article of manufacture, cellulose bulking material adapted foruse in explosive compositions, and composed essentially of the washedand comminuted pith of a plant of the genus Hibiscus.

3. An explosive composition characterized by low density and includingnitroglycerin, ammonium'nitrate, and an absorbent for said nitroglycerinpresent in an amount between limits of substantially 1% and 25%, theabsorbent consisting, at least in substantial part, of washed andcomminuted pulp of a plant of the mallow family.

4. A low density dynamite consisting of nitroglycerin in a proportionsubstantially within the range of 10% to 15%, nitrates substantiallywithin the range of to %;a small amount I an inert ingredient, and'acellulose absorbe t material" substantially within the range of 10 o to25%, the last said material being formed e sentially of cleaned andcomminuted pith from a plant of the mallow family.

5. A high explosive including nitroglycerin substantially 10%, ammoniumnitrate substantially sodium compounds substantially 13%, a small amountof an inert mineral ingredient together with a cellulose absorbentcomprising the pith of a plant of the mallow family, the compositionbeing of such a density that a standard cartridge thereof weighs notsubstantially in excess of 145 grams.

I 6. A high explosive composition including nitroglycerin substantially14-15%, ammonium nitrate substantially 55-56%, sodium compounds in anamount of the order of 4-5%, a small amount of an inert mineralingredient, together with a cellulose absorbent suiiicient to make upthe remainder and substantially 24-26%, the

' greater portion of the absorbent comprising the pith of a mallowplant, and the composition being of such density that a standardcartridge thereof has a weight substantially within the range of '75 tograms.

7. An explosive composition comprising a liquid explosive nitric esterand mallow pith.

8. An explosive comprising a liquid explosive nitric ester, nitrates andmallow pith.

BRUCE W. MANNING.

